Retroreflective sheeting can comprise a thermoplastic cube layer having a front light-receiving surface and a rear retroreflecting surface. Light incident on the front surface passes through the transparent thermoplastic layer, impinges on the rear retroreflecting surface, and is reflected back out through the front surface in a predetermined direction (e.g., aligned with and/or parallel to the direction of incidence). In this manner, incident light can be used to illuminate markings, words, and other information in an otherwise dark environment.
In certain situations, the sheeting's visibility and/or conspicuity during daylight hours is important. If so, the retroreflective sheeting must possess sufficient daytime brightness. This brightness feature can be described in terms of the second of the tristimulus coordinates (X,Y,Z) and is often referred to as “cap-Y.” A day time brightness (or cap-Y) scale ranges from 0 for a perfectly black material to 100 for a perfectly white material.